It is well-known in the art to utilize a clutch to selectively provide rotational power to a vehicle accessory such as an air compressor or other reciprocating device. U.S. Pat. Nos. 4,648,805, 4,632,639, and 4,561,827 to Beaumont each relate to an air compressor having a piston driven by a crankshaft. The crankshaft is supplied with rotational power by a multi-plate clutch when the clutch is engaged. The multiplate clutch has a driving portion and a driven portion. The driving portion of the clutch is provided with rotational power by a driveshaft. The piston of the air compressor is actuated by the crankshaft. The air compressor is de-activated by disengaging the clutch.
Devices such as and similar to that of the Beaumont design provide adequate means for selectively powering a single vehicle accessory. However, it was soon learned that the constant rotational power being supplied to the driving portion of the clutch by the driveshaft could be more efficiently allocated. In other words, the driving portion of the clutch and the driveshaft are continuously rotating whether the clutch is engaged or not. This rotational power goes to waste whenever the clutch is disengaged. One solution to this problem is that the continuous rotation could be used to power a vehicle accessory that did not require selective engagement like an air compressor. U.S. Pat. No. 5,497,742 to Plantan and U.K. Patent Application 2176255 of Christmas each disclose devices which utilize a clutch and a hollow crankshaft to drive a reciprocating device. The crankshaft is hollow so as to accommodate an extension of the driveshaft to drive a second device such as an alternator or a pump. The reciprocating device is powered whenever the clutch is engaged, but the second device is powered continuously. Both references disclose use of a multi-plate clutch.
The devices of the Plantan patent and the Christmas application suffer from significant disadvantages. First, their use of multi-plate clutches increases the complexity and cost of the system while decreasing the reliability, ease of installation, and ease of maintenance of the system. A further disadvantage of devices such as those disclosed by Plantan and Christmas is that disassembly of the device for maintenance or repair of the multi-plate clutch is burdensome and time-consuming due to the complexity in the way in which the clutch is mated to the vehicle accessory. This disadvantage exacerbates the problems relating to the complexity of the clutch itself. What is needed, therefore, is a device for powering vehicle accessories which addresses these shortcomings in the prior art.
The problems stemming from the multi-plate clutch design were addressed and reduced by the introduction of cone clutch systems. There are many examples of cone clutch systems in the mechanical arts. U.S. Pat. No. 4,226,318 to Morgan discloses a cone clutch that is hydraulically actuated and is representative of the general design of cone clutch systems. The cone clutch includes a female clutch member and a male clutch member. The female clutch member has a conically shaped annular inner surface. The male clutch member has a conically shaped annular outer shaped that is designed to mate with the female clutch member's inner surface. An input driveshaft, which is the source of rotational power in the system, is connected to the male clutch member. Depending on the intended application of the clutch system, the male clutch member can be urged into either engagement or disengagement with the female clutch member by, for example, coil springs. The female clutch member is attached to an output shaft or fabricated as a single, unitary piece with the shaft member. Thus, rotational power is provided by the input driveshaft which drives the male clutch member. When the male clutch member is engaged with the female clutch member, that is, when the annular, conical surfaces are in contact, rotational power is transmitted to the female clutch member and therefore also to the output shaft.
U.S. Patent Application Pub. 2004/0159524 of Carpenter et al. discloses a cone clutch for use with an air compressor. The Carpenter et al. system has a female cone member coupled to a crankshaft and a male cone member coupled to a driveshaft. The crankshaft drives an air compressor. The Carpenter et al. application discloses that a variety of accessories could be driven by the driveshaft simultaneously with the air compressor by mounting them on the input end of the driveshaft.
Other references disclose various applications of and improvements to cone clutch systems. U.S. Pat. No. 4,880,407 to Carton-Bacon discloses a cone clutch system which utilizes a layer of friction material between the conical surfaces of the clutch members. U.S. Pat. No. 4,805,706 to Stone discloses a rotary impact apparatus for use with an electric drill which utilizes a cone clutch. U.S. Pat. No. 6,960,107 to Schaub et al. discloses a marine transmission which uses a cone clutch to selectively transmit torque between a forward gear and a reverse gear. These and the above-mentioned documents are hereby incorporated by reference.
However, problems still remain in the art relating to the difficulty in attaching and integrating the clutch system to the vehicle accessories. As seen in the U.S. Pat. No. 4,648,805 Beaumont patent, attaching the multi-plate clutch assembly is a multi-step operation. First, a conical washer assembly and the clutch member are placed in the hollow clutch member. Then the clutch plates are introduced as well as an end member. The pre-load on the conical washer assembly is then set and the end member is secured by welding. This completed sub-assembly is placed in the clutch housing. The drive input shaft is then fed through the clutch plates with the splines to engage a bearing. Finally, a final bearing and an end cap are added to the assembly.
In the device disclosed by the Carpenter et al. application, access to the clutch for maintenance or repair purposes would also be difficult. If an accessory were to be driven by the driveshaft in addition to the air compressor on the input end of the driveshaft as disclosed, this would impede access to the clutch. In order to access the clutch the additional accessory would most likely be in the way or even be mounted on the clutch casing.
The Plantan patent and the Christmas application suffer from the additional disadvantage that their clutch components and first vehicle accessory components are intermingled. The driveshafts disclosed in each consist of a single piece which extends through the clutch and the crankshaft to the second device to be supplied with continuous power. Because of this design, repair and maintenance service to either the accessories or the clutch will disable the entire assembly.
The designs of the prior art cost valuable time whenever repair, maintenance, or replacement is needed. This is due not only of the increased complexity of the multi-plate clutch design, but also the lack of a simple interface between the clutch system and the vehicle accessory. What is needed, then, is a device for driving multiple vehicle accessories that is simple to assemble, maintain, repair, and install. In particular, a device is needed having the aforementioned characteristics as well as the capability to selectively power at least one vehicle accessory while simultaneously providing continuous power to at least one other vehicle accessory.